Landing gear for semitrailers

ABSTRACT

A landing gear for semitrailers includes a two-speed single reduction gear assembly having fewer, smaller, and simpler parts, resulting in a compact single reduction gear assembly and cost efficient landing gear unit with a unique clutch-shifting mechanism to provide for shifting from one ratio to another. The single reduction gear assembly is disposed on and about vertically offset input and output shafts further resulting in an easy to crank and shift landing gear unit capable of achieving standard crank handle turn to vertical leg travel distance ratios. The low gear or low speed ratio of the landing gear unit can be varied within a broad range during manufacture, if desired, generally without increasing the overall size or complexity of the two-speed single reduction gear assembly. The landing gear can further include a universal mounting feature and is durable and simple to use.

FIELD OF THE INVENTION

The invention relates to landing gear for semitrailers, and inparticular to a landing gear having a single reduction gear assembly.More particularly, the invention relates to such a landing gear whichachieves standard crank handle turn to vertical travel distance ratioswith a two-speed, single-reduction gear assembly, which utilizes fewer,simpler, and smaller parts to achieve such standard ratios resulting ina relatively compact, cost-effective single reduction gear assembly,featuring a unique shift-clutching mechanism which reduces the number ofparts and reduces cost while making it easier to shift between high andlow speeds.

BACKGROUND

Landing gear for semitrailers have heretofore been and will presumablycontinue to be a high volume product, with estimated sales in the UnitedStates normally exceeding 300,000 sets per year and generating income ofmore than 50 million dollars. The high demand for landing gear isdirectly related to the use of semi-trailers pulled by truck tractors asa primary means of shipping goods in the United States.

A conventional two-speed landing gear consists of a pair of gear-driven,laterally spaced, telescopic legs which are mounted on and depend from afront end of the semitrailer which engages the truck tractor.

Landing gear, and particularly two-speed landing gear, are used inassociation with semitrailers in the following manner. A typicalscenario begins with the operator of a truck tractor dropping off thesemi-trailer at a location such as a dock for loading or unloading ofthe semitrailer. This semitrailer is retrieved when loading or unloadingis completed, often by another tractor. When disconnecting afterpositioning the semitrailer in the desired location, the truck operatormanually turns a crank handle to extend the legs until the legs engagethe ground. The operator typically uses the high gear or high speed ofthe two-speed gear assembly to quickly extend the landing gear legs fromthe retracted position to the extended position where the legs contactthe ground. It should be noted that when the landing gear assembly isengaged in high gear, quick traversal of a vertical distance can beaccomplished due to the low ratio of crank handle turns to inches ofvertical leg travel distance afforded by the high gear, which ratiousually is from about 2 to about 5 depending on the unit being utilized.However, the tradeoff for such a low ratio achieved in high gear is alower mechanical advantage than that which can be achieved in a lowgear. In practical terms, this means that the truck operator cannotraise or lower a load in high gear. In low gear the ratio of crankhandle turns to distance traveled is higher, usually from about 15 toabout 50, but a higher mechanical advantage is enjoyed. This enables thetruck operator to raise or lower loads in low gear that could not bemoved in high gear, albeit at a slower pace than if such loads could bemoved in high gear. In order to pull the truck tractor away from thestationary semitrailer, the operator must disengage the dependingkingpin of the semitrailer from the fifth wheel of the truck tractor bydisengaging the fifth wheel jaws. Since the tractor is spring-biased inan upward direction, it is desirable to raise the semitrailer to relievesome of the load allowing the tractor to pull away from the semitrailermore easily. Therefore, the operator may shift the gear assembly to lowgear in order to further extend the landing gear legs and raise all orpart of the load of the semitrailer from the fifth wheel. Afterreleasing the movable jaws of the fifth wheel, the tractor is disengagedfrom the semitrailer.

When an operator picks up a semitrailer which has been loaded orunloaded, he or she must back the truck tractor fifth wheel under thesemitrailer and engage the kingpin. If the semitrailer was resting on astable surface such as concrete, and a similar tractor is utilized, thenecessary clearance to allow coupling most likely still exists betweenthe ground and the kingpin, and the operator merely will back the trucktractor under the semitrailer engaging the kingpin. The operator willshift the landing gear into low gear to lower the load onto the tractor,then shift into high gear and quickly retract the legs to provideclearance for vehicle operation. More particularly, the legs arepositioned approximately one foot off of the ground to provide clearancefor over-the-road travel. However, if the semitrailer was left on arelatively unstable surface such as soft ground or blacktop, thesemitrailer legs sometimes sink into the ground under the load of thetrailer between the drop off and pickup times. If this is the case, orif a higher tractor is employed, prior to backing the truck tractorunder the semitrailer the operator must further extend the legs to raisethe trailer to provide sufficient clearance between the ground and thekingpin. This requires the operator to shift the landing gear into lowgear to gain mechanical advantage to raise the trailer. After couplingto the tractor and lowering the trailer load onto the tractor using lowgear, the operator then will proceed as described above to retract thelegs in high gear to position the legs for over-the-road travel.

As expected, in view of the potential income accruing from possiblesales of landing gear units, manufacturers of the landing gear arecontinually attempting to improve their products to present a moreeconomical landing gear having improved performance features, in orderto gain a larger share of the landing gear market.

SUMMARY OF THE INVENTION

Objects of the present invention include providing a landing gear forsemitrailers having a two-speed single reduction gear assembly ortransmission, in which the gear assembly or transmission is comprised offewer, smaller and simpler parts thereby making it easier to manufactureand assemble and further resulting in an assembly which is compact andcan be contained in a smaller gear box, wherein all of the above factorscontribute to a lower overall cost of the landing gear unit.

Another object of the invention is to provide such a landing gear whichis easier to crank and shift, and which can be universally mounted.

A further object of the invention is to provide such a landing gearcapable of achieving commercially standard crank handle turn to verticalleg travel distance ratios, wherein the low speed ratio could be fixedwithin a broad range during manufacture, if desired, generally withoutincreasing the overall size or complexity of the two-speed singlereduction gear assembly.

A still further object of the invention is to provide a landing gearwhich is durable and simple to use.

These objects are obtained by the two-speed landing gear assembly for asemitrailer of the present invention, comprising, first and secondvertically extendable and retractable supports or upright telescopiclegs mounted in a laterally spaced relationship generally adjacent to afront end of said semitrailer; an input shaft rotatably mounted on saidfirst leg, said input shaft being axially movable or translatablebetween a first position for high-speed operation and a second positionfor low-speed operation; an output shaft rotatably mounted on said firstleg, said output shaft being axially parallel to said input shaft andspaced therefrom, said output shaft being operatively connected to aninput shaft rotatably mounted on said second leg; a small radius piniongear on said input shaft for transmitting rotary motion from said inputshaft to said output shaft; an intermediate gear on said output shaft,said intermediate gear having teeth which are engaged by teeth of saidpinion gear when said input shaft is in the second position forlow-speed operation; a second gear on said output shaft, said secondgear having a smaller diameter than said intermediate gear; a high-speeddrive gear supported on said input shaft, said high-speed drive gearhaving means enabling synchronous rotation with the input shaft when theinput shaft is in the first position for high-speed operation; and meansfor transmitting rotary motion from said output shaft to operate saidtelescopic legs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of the two-speed singlereduction gear assembly of the cranking leg of the landing gear of thepresent invention, shown adapted for mounting on an outboard position ona semitrailer frame;

FIG. 1A is a fragmentary perspective view of the two-speed singlereduction gear assembly of the cranking leg of the landing gear of thepresent invention, shown adapted for mounting on an inboard position ona semitrailer frame;

FIG. 1B is a fragmentary perspective view of the two-speed singlereduction gear assembly of the cranking leg of the landing gear of thepresent invention, shown adapted for universal mounting either on aninboard or an outboard position on a semitrailer frame;

FIG. 2 is a section taken on line 2--2 of FIG. 1, showing the singlereduction gear assembly engaged in low gear or the low speed position;

FIG. 2A is a view similar to FIG. 2, showing the gear assembly shiftedoutwardly and engaged in high gear or the high speed position;

FIG. 3 is an exploded fragmentary perspective view, with portions brokenaway and hidden parts shown by dashed lines, of the gear assembly ofFIG. 2;

FIG. 4 is a fragmentary perspective view, with portions broken away, ofthe two-speed single reduction gear assembly of the landing gear of thepresent invention, showing the gears engaged in low gear as in FIG. 2;

FIG. 4A is a view similar to FIG. 4, showing the gear assembly engagedin high gear as in FIG. 2A;

FIG. 5 is a side elevation view of a semitrailer shown disengaged from atruck tractor, and having the landing gear of FIG. 1 mounted thereon andsupporting the front end of the semitrailer;

FIG. 5A is a view looking in the direction of arrows 5A of FIG. 5;

FIG. 5B is a view similar to FIG. 5A, showing the landing gear of FIG.1A mounted on an inboard position on the semitrailer frame;

FIG. 6 is an exploded fragmentary perspective view, with hidden partsshown by dashed lines, of the gear assembly of the opposite-side leg ofthe landing gear of the present invention, shown adapted for mounting onan outboard position on a semitrailer frame;

FIG. 6A is a fragmentary perspective view of the gear assembly of theopposite-side leg of FIG. 6, showing the manner in which the gears mesh;

FIG. 7 is a side elevation view of an alternative embodiment of theinvention including an input shaft, an output shaft, and an intermediateshaft, with the input shaft shown at a position corresponding tolow-speed operation;

FIG. 7A is a view similar to FIG. 7, showing the input gear in aposition corresponding to high-speed operation.

Similar numerals refer to similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The landing gear for semitrailers of the present invention is shown inits intended use in FIGS. 5 and 5A and is indicated generally at 10.Landing gear 10 generally includes a pair of vertically extendable andretractable supports in the form of upright, spaced, parallel crankingand opposite-side legs 11 and 12, respectively, which depend from thefront end of a semitrailer 21. In the embodiment shown in FIGS. 5 and5A, cranking leg 11 is disposed on the left or driver's side of thesemitrailer 21 and opposite-side leg 12 is positioned on the right orcurb-side of the semitrailer. However, it is understood that crankingleg 11 could be placed on the curb-side of the semitrailer andopposite-side leg 12 could be placed on the driver's side withoutaffecting the concept of the present invention. Hereafter, cranking sideand opposite-side legs 11 and 12 will be referred to as the left ordriver's side and right or curb-side legs, respectively. Each leg 11, 12includes a lower tube 13 telescopically disposed (FIGS. 2, 3 and 6)within an upper tube 14, in a manner well known to the art and to theliterature. A foot 15 is connected to the lower end of lower leg tube 13in a conventional manner.

A pair of crossing transverse brace bars 22 (FIG. 5A) each is attachedat one of its ends to a frame 20 of semitrailer 21 and at the other ofits ends to an opposite leg 11, 12, respectively, for generallystabilizing the legs against side thrust forces and the like. A pair oflongitudinal brace bars 23 (FIG. 5), each is attached at one of its endsto upper tube 14 of a respective one of legs 11, 12, and at the other ofits ends to semitrailer frame 20.

With regard to the internal components of left or driver's side 11, anut 25 is fixed on the upper end of lower leg tube 13 for threadablyreceiving a vertical elevating screw shaft 26 (FIGS. 2 and 4) whichincludes a threaded lower shaft 24 and a reduced diameter, integralunthreaded upper shaft 27. A shoulder 28 is formed at the interface ofupper and lower shafts 27 and 24, respectively. An annular collar 29bears on shoulder 28, and an annular thrust bearing 30 rests on collar29 about upper shaft 27. A floor base 31 rests on bearing 30 (and nut25) and is disposed about upper shaft 27 which passes through acontinuous opening 32 formed in the floor base. Floor base 31 is weldedto the inside surfaces of upper leg tube 14. An annular spacer 16 iswelded to the top of floor base 31 about upper shaft 27. A hardenedthrust washer 33 is disposed on upper shaft 27 and rests on the uppersurface of spacer 16. A bevel gear 34 is slidably engaged on upper shaft27, and rotary motion is transmitted to upper shaft 27 by a pin 35 whichcouples bevel gear 34 to the upper shaft in a manner familiar to thosehaving ordinary skill in the art. Hardened thrust washer 33 provides awear surface for contact by bevel gear 34 and coupling pin 35.

In accordance with one of the main features of the present invention, ametal gear case indicated generally at 42, together with the inboardwall of upper leg tube 14, generally define a gear case compartment 43(FIGS. 1, 2, 3 and 5A) which is integral with the leg structure 11. Morespecifically, gear case 42 is comprised of four primary components,namely, a pair of bent metal flanges 44 attached by bead welds in aspaced relationship on the upper inboard portion of upper leg tube 14, acover 45 and a cap 46. Cover 45 is formed with a plurality of raisedbosses 48 which are alignable with and snugly fit within respective onesof a plurality of vertically spaced openings 47 formed in flanges 44.Each boss 48 is formed with a threaded recess 49 for threadablyreceiving screws 52 for securing cover 45 to flanges 44. Cap 46 ispositioned over the upper open ends of upper leg tube 14 and gear case42, and is secured thereon by any suitable means such as self-tappingscrews (not shown). Cap 46, together with floor base 31 and the walls ofupper leg tube 14 define an upper compartment 41 of upper leg tube 14. Agasket 50 of any suitable type such as one formed of an elastomericmaterial is placed or applied at the interface of cap 46 and upper legtube 14 and cover 45 in a usual manner. Gasket 50 and cap 46, incooperation with cover 45, bent metal flanges 44, and upper leg tube 14,effectively protect the two-speed single reduction gear assembly oflanding gear 10 contained within upper compartment 41 and gear casecompartment 43 of upper leg tube 14, from outside elements such as dirt,moisture, etc., which could interfere with the efficient operation ofthe gear assembly or transmission. The bent metal flanges 44 and cap 46of gear case 42, due to the small number, size and compact orientationof the components contained therein, are formed by a metal bendingprocess as compared to many prior art gear boxes which must be formed bymore expensive metal stamping processes due to the larger number, sizeand/or less compact orientation of the components contained therein.More specifically, the components of the two-speed single reduction gearassembly or transmission of the landing gear of the present inventioncontained in gear case 42, are all generally adjacent to the inboardwall of upper leg tube 14, and in particular do not extend beyond thewidth of the outboard wall. Therefore, gear case bent metal flanges 44and cap 46 formed by mere bending, together with gear case cover 45,cooperate with the inboard wall of upper leg tube 14 to adequately coverthe components contained therein. In contrast, many prior art landinggear assemblies extend beyond the width of the adjacent upper leg tube,thus requiring, in many cases, a two-piece gear case which must bestamped or otherwise machined so that the two pieces fit togetherproperly and adequately protect the components contained therein fromoutside elements. It also is important to note that cover 45 of gearcase 42 has a dual function. More particularly, the outer or protrudingends of cover 45 are each formed with a plurality of vertically spacedopenings 51 for receiving fastening means 18 such as bolts or the like,for attachment of leg 11 to an outboard surface 19 of frame 20 ofsemitrailer 21 (FIGS. 5 and 5A).

An output shaft 60 (FIGS. 2 and 4) has first and second ends 61 and 62mounted in upper compartment 41 and gear case compartment 43 of upperleg tube 14, and extends outwardly therefrom in an inboard direction.First and second ends 61 and 62 of output shaft 60 are rotatably mountedin bushings 63 and 64, respectively, which in turn are frictionallyfitted in aligned openings 65 and 66 formed in the outboard wall ofupper leg tube 14 and in gear case cover 45. It should be noted thatbushing 63 is closed on its outboard end and receives first end 61 ofoutput shaft 60, while bushing 64 is formed with a continuous openingallowing second end 62 of output shaft 60 to pass therethrough in aninboard direction for operative connection with the gear assembly ofcurb-side leg 12. As shown in at least FIGS. 1, 1A, 1B and 2, the upperoutboard wall is spaced apart from the inboard wall and has a verticalsurface which is substantially free of an external exterior gear box.

An integral one-piece combination gear 70 is mounted on second end 62 ofoutput shaft 60 within upper compartment 41 and gear case compartment 43of upper leg tube 14, by a pin 71 in a conventional manner. Moreparticularly, the combination gear includes an intermediate gear 72, asecond gear 73 which is a reduced diameter gear with respect tointermediate gear 72 and is disposed abuttingly adjacent to theintermediate gear in an outboard direction, and bevel pinion 74 which inturn is formed abuttingly adjacent to and outboard from gear 73. Asnoted above, combination gear 70 extends between and is contained withinupper compartment 41 and gear case compartment 43 of upper leg tube 14.Specifically, a cutout 69 (FIG. 3) is formed in the inboard wall ofupper leg tube 14 for communication between upper compartment 41 andgear case compartment 43. Intermediate gear 72 of combination gear 70 iscontained entirely within gear case compartment 43, bevel pinion 74 ofcombination gear 70 is contained entirely within upper compartment 41,and gear 73 disposed therebetween straddles cutout 69 and is partiallycontained within upper compartment 41 and gear case compartment 43.

An input shaft 75 having first and second ends 76 and 77, respectively,is slidably rotatably mounted in upper compartment 41 of upper leg tube14 and in gear case compartment 43, and is disposed below and offsetfrom output shaft 60. More specifically, a pair of bushings 78 and 79are frictionally fitted in aligned openings 80 and 81, respectively,formed in the outboard wall of upper leg tube 14 and in gear case cover45. Second end 77 of input shaft 75 terminates in a reduced diameterstud 82 which is slidably rotatably mounted in bushing 79 which isclosed on its inboard end. Bushing 78 is formed with a continuousopening allowing first end 76 of input shaft 75 to pass therethrough andextend outwardly from upper leg tube 14 in an outboard direction. Apinion gear 83 is formed in second end 77 of input shaft 75 adjacent toreduced diameter stud 82. Spacer 16 is coped or provided with atransverse cylindrical recess which provides clearance for input shaft75 to permit a compact structure wherein the input shaft and outputshaft are supported on the inboard and outboard walls of leg 11 andbetween the forward and rearward walls of leg 11.

A high-speed drive gear 85 is supported on input shaft 75 and is formedwith a hub 90 which extends outwardly from gear 85 in an outboarddirection. Hub 90 in turn is formed with a continuous axial opening 86and further has internal teeth or a plurality of axially extendingspline slots 84 formed in its internal surface. Hub 90 is rotatablymounted in a bushing 87 which in turn is frictionally fitted in anopening 88 formed in the inboard wall of upper leg tube 14, whereinopening 88 is aligned with openings 80, 81, so that second end 77 ofinput shaft 75 is slidably rotatably mounted in continuous hub opening86. Gear 85 is maintained in position, and in particular is preventedfrom moving in an inboard direction, by a spacer 89 welded to theoutboard face of gear case cover 45. A transverse continuous cylindricalopening 92 is formed in a generally central portion of input shaft 75. Adetent spring 93 having a detent ball 94 disposed on each of its ends isfitted within opening 92 for positively engaging first and secondannular recesses 95 and 96, respectively, formed in the interior surfaceof bushing 78. A transverse continuous cylindrical opening 97 is formedin first end 76 of input shaft 75, for receiving a bolt 98 (FIG. 1) orother means for fastening a crank handle 99 to input shaft 75.

As shown in FIG. 5A, a connecting shaft 106 extends between and issecured at each of its ends by fasteners 107 and 108 such as bolts orthe like, to second end 62 of output shaft 60 of leg 11 and to an inputshaft 109 of leg 12, respectively. The internal components contained inthe right or curb-side leg 12 of landing gear are similar in manyrespects to those contained in the lower and upper leg tubes 13, 14 ofleft or driver's side leg 11, and are illustrated in FIGS. 6 and 6A.Input shaft 109 includes first and second ends 111 and 112,respectively, which are rotatably mounted in bushings 113 and 114, whichin turn are frictionally fitted in aligned openings 115 and 116 formedin the inboard and outboard walls of upper leg tube 14. A bevel pinion117 is securely mounted on second end 112 of output shaft 109 by a pin118 in a conventional manner. A spacer tube 119 maintains bushings 113,114 and bevel gear 117 in their intended positions to prevent lateralmovement of input shaft 109. Bevel pinion 117 meshes with a bevel gear120 which in turn is disposed on an elevating screw shaft 121 in amanner similar to bevel gear 34 of driver's side leg 11. The structureand manner of mounting screw shaft 121 in curb-side leg 12 is similar tothat described above for the mounting of screw shaft 26 in driver's sideleg 11, which is hereby fully incorporated by reference. Leg 12 ismounted on an outboard position on semitrailer frame 20 in the followingmanner. A pair of bent metal flanges 126 are attached by bead welds in aspaced relationship on the upper inboard portion of upper leg tube 14. Afastening plate 127 is formed with a plurality of raised bosses 128which are alignable with and snugly fit within respective ones of aplurality of vertically spaced openings 129 formed in flanges 126. Eachboss 128 is formed with a threaded recess (not shown) for threadablyreceiving screws 131 for securing fastening plate 127 to flanges 126.Fastening plate 127 also is formed with an opening 133 to allow forpassage of input shaft 109 into leg 12. A cap is positioned over theupper open end of upper leg tube 14, and is secured thereon by anysuitable means such as self-tapping screws (not shown), in a mannersimilar to that described above for leg 11. The outer or protruding endsof fastening plate 127 each is formed with a plurality of verticallyspaced openings 132 for receiving fastening means 18 such as bolts orthe like, for attachment of leg 12 to outboard surface 19 of frame 20 ofsemitrailer 21 (FIG. 5 and 5A).

If it is desired to mount legs 11 and 12 on an inboard surface of asemitrailer frame (FIG. 5B), a flange plate 123 is attached to anoutboard surface of upper leg tube 14 by any suitable means such aswelding (FIG. 1A). Each protruding end of flange plate 123 is formedwith a plurality of openings 124 for receiving fastening means 125 suchas bolts or the like, for attachment of legs 11, 12 to semitrailer frame122. If desired, legs 11 and 12 can each have the outboard and inboardmounting structures described above mounted thereon (FIG. 1B), so thatlegs 11 and 12 of landing gear 10 may be attached either to the outboardor inboard surfaces of a semitrailer frame.

Landing gear 10 of the present invention is operated in the followingmanner when it is desired to work the landing gear in low gear or lowspeed, wherein the ratio of turns of crank handle 99 to verticaldistance of travel of legs 11, 12 is high, but wherein the mechanicaladvantage enjoyed by the operator of the landing gear also is high. Moreparticularly, this ratio is from about 15 to about 50, desirably fromabout 20 to about 40, and preferably from about 25 to about 35 turns perinch, which generally are standard ratios. Landing gear 10 is shown inthe low gear in FIGS. 2 and 4. To lower upper leg tube 14 with respectto lower leg tube 13 of the driver's side and curb-side legs 11 and 12,respectively, in low-speed, input shaft 75 is manually slidably moved toits inwardmost position by applying a pushing force to crank handle 99,so that detent balls 94 are positively engaged with second annularrecess 96. Crank handle 99 and attached input shaft 75 then are manuallyrotated in a clockwise direction as shown by the arrow in FIG. 4,whereby pinion gear 83 meshes with the teeth of intermediate gear 72 ofcombination gear 70 for rotating the intermediate gear in acounterclockwise direction. In transmitting the rotary motion of inputshaft 75 from pinion gear 83 to intermediate gear 72, a single reductionhaving a magnitude of, for example, about 6.6:1 is achieved. As is wellknown to those of ordinary skill in the art, in practical terms, such areduction means that intermediate gear 72 is rotating about 6.6:1 timesslower than input shaft 75, but a gain in mechanical advantage of amagnitude of about 6.6 is at the same time realized by the operator oflanding gear 10. That is, due to the reduction achieved in transmittingrotary motion from pinion gear 83 to intermediate gear 72, the operatorwill find that crank handle 99 is about 6.6 times easier to turn thanwithout such a reduction. Attached counterclockwise rotating bevelpinion 74 meshes with bevel gear 34 to rotate the bevel gear andattached screw shaft 26 in a clockwise direction.

A second reduction having a magnitude of, for example, about 2:1 occursin going from bevel pinion 74 to bevel gear 34, resulting in an overallreduction of 13.3, meaning that screw shaft 26 turns about 13.3 timesslower than input shaft 75 in low gear. However, landing gear 10 of thepresent invention would be customarily referred to in the art andliterature as a single reduction assembly based on the reduction whichtakes place in gear case compartment 43 between pinion gear 83 andintermediate gear 72. Most prior art landing gear have a single ordouble reduction which takes place in the gear case, as well as anotherreduction which takes place at the junction of the output shaft and theelevating screw shaft. However, such landing gear generally areidentified as single reduction or double reduction based on the numberof reductions which take place exclusive of the reduction at thejunction of the output shaft and elevating screw shaft. Therefore, thetotal reduction of about 13.3, when combined with the screw lead pitchof about 2.25 of threaded lower shaft 24 of elevating screw shaft 26,results in a low gear ratio of crank handle turns to vertical traveldistance of 13.3 times about 2.25 equalling about 30 turns per inch.This means that, in low gear, for every 30 turns of crank handle 99,screw shaft 26 will travel one inch in vertical distance. Although screwshaft 26 is turning about 13.3 times slower than input shaft 75, theoperator enjoys a theoretical mechanical advantage of a magnitude ofabout 30. For a typical crank handle having, for example, about a16-inch lever (as measured by the radial displacement of the handle 99from the rotational axis of the input shaft 75), the handle movescircumferentially through a distance of about 100 inches per revolution,which means that crank handle 99 theoretically turns about 3,000 timeseasier than it would without the landing gear mechanism. Afterfrictional losses are accounted for, the net mechanical advantage of theentire mechanism is about 900 to 1. Rotation of screw shaft 26 in nut 25in the counterclockwise direction causes upward movement of the screwshaft in the nut resulting in retraction of lower leg tube 13 withinupper leg tube 14.

The foregoing example is only illustrative; the gear reduction betweenthe pinion gear 83 and the intermediate gear can typically range fromabout 2:1 or 2.5:1 to about 8:1. Similarly, the second reduction betweenthe bevel pinion 74 and bevel gear 34 can typically range from about1.5:1 to about 2.5:1 Likewise, the effective screw pitch of 2.25 is onlyillustrative; with typical screw pitches ranging from 1.5 turns per inchto 4 turns per inch. Effective screw pitch refers to the number of screwrevolutions required to achieve an axial screw displacement of one inch.

Output shaft 60 simultaneously rotates connecting shaft 106 in aclockwise direction, which in turn rotates input shaft 109 of leg 12 ina clockwise direction as shown in FIG. 6A. Attached clockwise-rotatingbevel pinion 117 meshes with bevel gear 120 to rotate the bevel gear andattached screw shaft 121 in a counterclockwise direction in a mannersimilar to the rotation of screw shaft 26 of driver's side leg 11, forretracting lower leg tube 13 with respect to upper leg tube 14. Ofcourse, it is understood that rotation of crank handle 99 in theopposite or counterclockwise direction results in opposite movement ofall of the above-described components of landing gear 10, which in turnsresults in extension of lower leg tube 13 from upper leg tube 14 in bothlegs 11, 12.

In accordance with another of the main features of the presentinvention, when it is desired to work landing gear 10 in high gear orhigh-speed, wherein the ratio of turns of crank handle 99 to verticaldistance of travel of legs 11, 12 is low, but wherein the mechanicaladvantage realized by the operator also is low, the landing gear isoperated in the following manner. The high gear ratio is from about 2 toabout 5, desirably from about 3 to about 4.5, and preferably from about4 to about 4.5 turns per inch, which generally are standard ratios.Landing gear 10 is shown in high gear in FIGS. 2A and 4A. To lower upperleg tube 14 with respect to lower leg tube 13 of the driver's side andcurb-side legs 11 and 12, respectively, in high speed, input shaft 75 ismanually slidably moved to its outwardmost position by applying apulling force to crank handle 99, so that detent balls 94 disengage fromsecond annular recess 96 and positively engage first annular recess 95.Such outward movement of input shaft 75 from the inwardmost positionshown in FIGS. 2 and 4 to the outwardmost position shown in FIGS. 2A and4A causes pinion gear 83 to retract within continuous opening 86 of hub90 of gear 85, whereby the outer ends of the gear teeth of pinion gear83 function as splines to slidably engage the internal teeth or splineslots 84 formed in the hub. It is important to note that the relativelysmall size of pinion gear 83, which must be moved through heavylubricating grease contained in gear case compartment 43 during shiftingbetween gear speeds, results in an apparatus with improved shiftingease. More particularly, this grease offers resistance to the movementof pinion gear 83 therethrough, and makes such movement particularlydifficult in cold weather conditions when the grease is more viscous.However, the small size of pinion gear 83 relative to many prior artgears which must be shifted through such lubricating grease,substantially reduces the effect of the grease resistance. Moreover, therelatively short horizontal distance between first and second annularrecesses 95 and 96 of about 5/8 inch, which is less than many prior artdevices which require an inward movement of a gear a distance of about11/4 inch to accomplish a similar shift from one gear speed to anothergear speed, also aids in improving the shifting ease of the apparatus ofthe present invention. Thus, such a spline shifting or "clutch shifting"apparatus is more efficient than many known prior art landing gearshifting apparatus, including "constant gear mesh" designs.

Crank handle 99 then is manually rotated in a clockwise direction asshown in FIG. 4A whereby clockwise rotating input shaft 75 rotatesattached pinion gear 83 in a clockwise direction, which in turn rotatesengaged hub 90 of gear 85. Clockwise rotating gear 85 in turn mesheswith and rotates gear 73 of combination gear 70, which in turn rotatesoutput shaft 60 and attached bevel pinion 74 in a counterclockwisedirection. Bevel pinion 74 meshes with bevel gear 34 to rotate the bevelgear and attached screw shaft in a counterclockwise direction. Asdiscussed above, the reduction in going from bevel pinion 74 to bevelgear 34 can, for example, be of a magnitude of about 2:1, which is theonly reduction or only significant reduction, which occurs in high gear.The gear ratio between the high-speed drive gear 85 and gear 73 istypically from about 1:1 to about 0.6:1, with a gear ratio of about 1:1being preferred. A 2:1 gear reduction between the bevel pinion 74 andbevel gear 34 and a 1:1 gear ratio between the high-speed gear 85 andgear 73, when combined with a screw lead pitch of about 2.25 of threadedlower shaft 24 of elevating screw shaft 26, results in a high gear ratioof crank handle turns to vertical travel distance of about 2 times about2.25, equalling about 4.5 turns per inch. More specifically, this meansthat in the high gear, for every 4.5 turns of crank handle 99, screwshaft 26 travels about one inch in a vertical direction, or faster thanin low gear. However, it should be noted that when landing gear 10 is inhigh gear or high-speed, the operator conversely only enjoys an overalltheoretical mechanical advantage of a magnitude of about 450 with screwshaft 26 turning only about 2 times slower than input shaft 75, ascompared to a theoretical mechanical advantage of about 3000 in lowgear. The net mechanical advantage of the mechanism after accounting forfrictional losses is about 135 in high gear. Rotation of screw shaft 26in nut 25 in the counterclockwise direction causes downward movement ofthe screw shaft in the nut resulting in retraction of lower leg tube 13and upper leg tube 14. Operatively connected curb-side leg 12simultaneously operates in a similar manner as described above for thedescription of the operation of landing gear 10 in low speed. Of course,it is understood that rotation of crank handle 99 in the opposite orcounterclockwise direction results in opposite movement of all of theabove-described components of landing gear 10, which in turn results inextension of lower leg tube 13 from upper leg tube 14 in both legs 11,12.

Preferably, the ratio of turns of the input shaft to inches of travel ofthe telescoping legs is from about 4 to about 6 in high gear, and fromabout 18 to about 35 in low gear.

It should be noted and is understood that depending on whether screwshaft 26 and nut 25 are threaded in a right-hand or left-hand direction,rotation of crank handle 99 in a given direction will cause lower legtube 13 either to retract within or extend from upper leg tube 14.

While the present invention has been described in detail relative to thepreferred embodiment of the transmission or gear assembly which includesparallel input and output shafts wherein the output shaft has a bevelpinion 74 which engages bevel gear 34 to cause rotation of screw shaft27, it will be readily appreciated by those having ordinary skill in theart that additional shafts can be added to take advantage of theimproved shifting ease of the invention without departing from thespirit and scope of the invention. Specifically, one of the importantfeatures of the invention is the use of an axially movable input shaft75 having attached in fixed relationship thereto a relatively smallradius pinion gear 83 which together can be easily moved such as throughheavy lubrication grease to allow easy shifting between low and highspeed operation. As can be seen, for example in FIGS. 7 and 7A, the easeof shifting and other attributes of the invention can be achieved in amultiple shaft arrangement wherein an intermediate shaft 200 is used tooperatively couple an input shaft 202 to an output shaft 204. The inputshaft 202 is generally similar to the previously described input shaft75 and includes a pinion gear 206 (generally analogous to pinion gear83) which is secured in fixed relationship to input shaft 202. Ahigh-speed drive gear 210 is supported on input shaft 202 in a mannergenerally similar to the manner in which gear 85 is supported by shaft75 for the previously described embodiment. Gear 210 is formed with ahub 212 having internal gear teeth 214 or a plurality of spline slotswhich mesh with the teeth of pinion gear 206 when shaft 202 is in theposition for high speed operation as shown in FIG. 7A. Intermediateshaft 200 includes a larger diameter gear 216 having teeth which meshwith the teeth of pinion gear 206 when shaft 202 is in the position forlow-speed operation as shown in FIG. 7. Intermediate shaft 200 alsoincludes a smaller diameter gear 218 having teeth which mesh withexternal teeth 220 of high-speed drive gear 210 and with teeth of gear222 on output shaft 204. Output shaft 204 also has a bevel pinion 225fixedly secured thereto which is similar to the bevel pinion 74 of thepreferred embodiment shown in FIGS. 2-4A and which has teeth which meshwith the teeth of a bevel gear 228 fixed to a screw shaft 230 forraising and lowering of the telescoping legs. The alternative embodimentshown in FIGS. 7 and 7A is generally analogous to the preferredembodiment shown in FIGS. 1-6A except for the inclusion of an additionalshaft 204 and gear 222.

In summary, important features of the present invention include alanding gear for semitrailers having a two-speed single reduction gearassembly, in which the gear assembly is comprised of fewer, smaller andsimpler parts mounted on and about vertically offset input and outputshafts, resulting in an easy to manufacture and assemble, compact,low-cost landing gear unit. This reduction in the number, size andcomplexity of parts results in an easy to crank and shift unit capableof achieving standard crank-handle turn to vertical leg travel distanceratios, wherein the low speed ratio could be fixed within a broad rangeduring manufacture of the unit, if desired, without substantiallyincreasing the overall size or complexity of the two-speed singlereduction gear assembly. The landing gear of the present invention isdurable and simple to use, and can include a universal mounting feature.

While in accordance with the patent statutes the best mode and preferredembodiment has been set forth, the scope of the invention is not limitedthereto, but rather by the scope of the attached claims.

What is claimed is:
 1. A two speed landing gear assembly for asemitrailer, comprising:first and second upright telescopic legs mountedin a laterally spaced relationship generally adjacent to a front end ofsaid semitrailer and said first leg including an inboard wall opposingsaid second leg and a spaced apart outboard wall including an exteriorvertical surface; a first shaft rotatably mounted on said first leg,said first shaft being axially movable between a first position forhigh-speed operation and a second position for low-speed operation; asecond shaft rotatably mounted on said first leg, said second shaftbeing axially parallel to said first shaft and spaced therefrom; apinion gear on said first shaft for transmitting rotary motion from saidfirst shaft to said second shaft; a first gear on said second shaft,said first gear having teeth which are engaged by teeth of said piniongear when said first shaft is in the second position for low-speedoperation; a second gear on said second shaft, said second gear having asmaller diameter than said first gear; a high-speed drive gear supportedon said first shaft, said high-speed drive gear having an axial openingwith a plurality of axially extending spline slots on its internalsurface, said spline slots being configured so that the teeth of saidpinion gear engage the spline slots of said high-speed drive gear andthe teeth of said high-speed drive gear mesh with teeth of said secondgear on said second shaft when said first shaft is in said firstposition for high-speed operation; means for transmitting rotary motionfrom said second shaft to operate said telescopic legs; and saidexterior vertical surface being substantially free from an externalexterior gearbox.
 2. The assembly of claim 1, wherein a gear reductionof from about 2:1 to about 8:1 is achieved between said pinion gear andsaid first gear on said second shaft when said first shaft is in saidsecond position for low-speed operation.
 3. The assembly of claim 2,wherein a gear ratio of from about 1:1 to about 0.6:1 is achievedbetween said high-speed drive gear and said second gear on said secondshaft when said first shaft is in said first position for high-speedoperation.
 4. The assembly of claim 3, wherein said means fortransmitting rotary motion from said second shaft to operate saidtelescoping legs includes a bevel pinion mounted on said second shaft, abevel gear mounted on an upper end of an upright elevating screw shaftwhich is mounted within said first leg, a bevel pinion mounted on saidsecond leg, and a bevel gear mounted on an upper end of an uprightelevating screw shaft mounted within said second leg; wherein each ofsaid bevel pinions mesh with a corresponding one of said bevel gearsattached to a corresponding one of said elevating screw shafts tosimultaneously operate each of said telescoping legs when said secondshaft is caused to rotate.
 5. The assembly of claim 3, wherein saidfirst gear on said second shaft, said second gear on said second shaft,and said bevel pinion mounted on said second shaft are integrated into aone-piece combination gear, with said second gear being disposedabuttingly adjacent to said first gear, and said bevel pinion beingdisposed abuttingly adjacent to said second gear.
 6. The assembly ofclaim 5, wherein a metal gear box encases said pinion gear of said firstshaft mounted on said first leg, said one-piece combination gear, andsaid high-speed drive gear; and wherein the gear box and componentsencased therein are generally adjacent to said inboard wall and aredisposed inboard of said outboard wall.
 7. The assembly of claim 6,further comprising a crank handle secured to the outboard end of saidfirst shaft mounted on said first leg for manual rotation of said firstshaft, wherein an intermediate portion of said first shaft mounted onsaid first leg is formed with a transverse continuous cylindricalopening containing a detent spring and detent balls, wherein a sleeve ismounted on an outboard face of said gear case in alignment with anopening formed in said gear case, said sleeve having outboard andinboard annular recesses formed in an internal surface thereof, saidoutboard and inboard recesses being spaced apart, wherein said detentballs engage said outboard and inboard annular recesses when said firstshaft is in the first position and second position, respectively, forhigh-speed and low speed operation, respectively.
 8. The assembly ofclaim 7, wherein a flange plate is mounted on an inboard portion of eachof said first and second legs for mounting said landing gear assembly onan outboard surface of a semitrailer frame.
 9. The assembly of claim 7,wherein a flange plate is mounted on an outboard portion of said gearcase and forms the outboard portion of said gear case and is mounted onan outboard portion of said second leg, for mounting said landing gearassembly on an inboard surface of a semitrailer frame.
 10. The assemblyof claim 1, wherein said means for transmitting rotatory motion fromsaid second shaft to operate said telescopic legs includes a third shaftand at least one gear on said third shaft which meshes with at least onegear on said second shaft, said third shaft being axially parallel toeach of said first and second shafts and being spaced therefrom.
 11. Atwo-speed landing gear assembly for a semitrailer, comprising:a pair oflaterally spaced telescoping legs; a horizontally arranged input shaftrotatably and slidably mounted to a first of said legs, said input shafthaving a pinion gear fixed thereto, and said input shaft being axiallymovable between a first position for high-speed operation and a secondposition for low-speed operation; a high-speed drive gear supported onsaid input shaft at a fixed position relative to said first leg, saiddrive gear having an axial opening with a plurality of axially extendingspline slots on its internal surface which engage teeth on said piniongear of said input shaft when said input shaft is axially positioned forhigh-speed operation, thus providing for synchronous rotation of saidhigh-speed drive gear with said input shaft upon rotation thereof, anoutput shaft rotatably mounted on said first leg, said output shaftbeing axially parallel to said input shaft; a large-diameter gear fixedon said output shaft and having teeth which mesh with said pinion gearof said input shaft when said input shaft is axially positioned forlow-speed operation; a small-diameter gear fixed on said output shaftand having teeth which mesh with said high-speed gear when said inputshaft is axially positioned for high-speed operation; means fortransmitting rotary motion from said output shaft to operate saidtelescoping legs; a gear case supported on said first leg opposing saidsecond leg and which together with said leg houses said high speed drivegear, said large diameter gear, said input shaft pinion, said smalldiameter gear and said means for transmitting rotary motion; whereinsaid pinion gear is an integrally formed part of said input shaft;wherein said means for transmitting rotary motion from said output shaftto operate said telescoping legs includes a bevel pinion mounted on saidoutput shaft, a bevel gear mounted on an upper end of an uprightelevating screw shaft which is mounted within said first leg, a bevelpinion mounted on a second leg input shaft, and a bevel gear mounted onan upper end of an upright elevating screw shaft mounted within saidsecond leg; wherein each of said bevel pinions mesh with a correspondingone of said bevel gears attached to a corresponding one of saidelevating screw shafts to simultaneously operate each of saidtelescoping legs when said output shaft is caused to rotate.
 12. Theassembly of claim 11, wherein said large diameter gear, said second gearon said output shaft, and said bevel pinion mounted on said output shaftare integrated into a one-piece combination gear, with said second gearbeing disposed abuttingly adjacent to said large diameter gear, and saidbevel pinion being disposed abuttingly adjacent to said second gear. 13.The assembly of claim 12, wherein said input shaft and said output shaftare supported on the inboard and outboard walls of said first leg andare located between the forward and rearward walls of said first leg.14. The assembly of claim 13, wherein a gear reduction of from about 2:1to about 8:1 is achieved between said small radius pinion gear and saidlarge diameter gear when said input shaft is in said second position forlow-speed operation.
 15. The assembly of claim 14, wherein a gear ratioof from about 1:1 to about 0.6:1 is achieved between said high-speeddrive gear and said second gear on said output shaft when said inputshaft is in said first position for high-speed operation.
 16. Amultiple-speed landing gear assembly for a trailer comprising:at leastone-vertically extendable and retractable support including a bevelgear, an input shaft, and a transmission, said input shaft beingoperatively connected to said support by means of said transmissionwhereby rotation of said input shaft causes vertical extension andretraction of said support and said input shaft having a longitudinalaxis and being translatable along said axis between a first position anda second position, said transmission comprising; a pinion coaxiallymounted on said input shaft; a second shaft including a bevel piniongear, said shaft being connected with said support such that rotation ofsaid bevel pinion drives said bevel gear to cause vertical extension andretraction of said support, said second shaft being operatively coupledto a first drive gear which engages said coaxially mounted pinion whensaid input shaft is in said second axial position, said bevel gear beinglocated between said input shaft and said second shaft; a gear coaxiallymounted on said input shaft and having internal splines which engagesaid pinion to lock said coaxial gear in synchronous rotation with saidinput shaft when said input shaft is in a first axial position, saidtransmission including a second drive gear which is driven by saidcoaxial gear.
 17. A multiple-speed landing gear assembly as set forth inclaim 16, wherein said input shaft is parallel and non-coaxial with saidsecond shaft.
 18. A multiple-speed landing gear assembly as set forth inclaim 17, wherein said first axial position is a high-speed drive andsaid first drive gear has a larger gear ratio to said pinion than saidsecond drive gear to said gear coaxially mounted on said input shaft.19. A multiple-speed landing gear assembly as set forth in claim 16,wherein said transmission includes detente means which retain said inputshaft in said first or said second axial position.
 20. A multiple-speedlanding gear assembly as set forth in claim 16, further comprising athird shaft having thereon said first drive gear and said second drivegear, said third shaft being axially parallel to said input shaft andsaid second shaft and being spaced therefrom.
 21. A multiple-speedlanding gear assembly for a trailer comprising:at least one verticallyextendable and retractable support, an input shaft, an output shaftoperatively coupled to the support where the rotation of the outputshaft extends and retracts the support, and a transmission coupling saidinput shaft and said output shaft, said input shaft having alongitudinal axis and being translatable along said axis between a firstposition and a second position, said transmission comprising; a pinioncoaxially mounted on said input shaft, a drive gear coaxially mounted onsaid output shaft, an intermediate shaft having a first gear engaged bysaid pinion when said input shaft is in the second position and a secondgear which engages the drive gear on the output shaft, and said inputshaft having a large diameter gear which engages the second gear of theintermediate shaft and which has internal spline slots which are engagedby said pinion when said input shaft is in the first position.
 22. Amultiple-speed landing gear assembly as set forth in claim 21, whereinthe support has a bevel gear and the output shaft has a bevel pinionwhich engages the bevel gear to cause the support to extend or retract.23. A multiple-speed landing gear assembly as set forth in claim 22,wherein said first gear on the intermediate shaft is a large diametergear and the second gear is a small diameter gear.
 24. A multiple-speedlanding gear assembly as set forth in claim 22, wherein the second gearof the intermediate shaft engages both the large diameter gear of theinput shaft and the drive gear of the output shaft.
 25. A multiple-speedlanding gear assembly as set forth in claim 24, wherein the transmissionis contained within a housing.
 26. A two speed landing gear assembly fora semitrailer, comprising:first and second upright telescopic legsmounted in a laterally spaced relationship generally adjacent to a frontend of said semitrailer; a first shaft rotatably mounted on said firstleg, said first shaft being axially movable between a first position forhigh-speed operation and a second position for low-speed operation; asecond shaft rotatably mounted on said first leg, said second shaftbeing axially parallel to said first shaft and spaced therefrom; apinion gear on said first shaft for transmitting rotary motion from saidfirst shaft to said second shaft; a first gear on said second shaft,said first gear having teeth which are engaged by teeth of said piniongear when said first shaft is in the second position for low-speedoperation; a second gear on said second shaft, said second gear having asmaller diameter than said first gear; a high-speed drive gear supportedon said first shaft, said high-speed drive gear having an axial openingwith a plurality of axially extending spline slots on its internalsurface, the teeth of said pinion gear engaging the spline slots of saidhigh-speed drive gear and teeth of said high-speed drive gear meshingwith teeth of said second gear on said second shaft when said firstshaft is in said first position for high-speed operation; means fortransmitting rotary motion from said second shaft to operate saidtelescopic legs which means includes a bevel pinion mounted on saidsecond shaft, a bevel gear mounted on an upper end of an uprightelevating screw shaft which is mounted within said first leg; whereinsaid first gear on said second shaft, said second gear on said secondshaft, and said bevel pinion mounted on said second shaft are anintegrated one-piece combination gear, with said second gear beingdisposed abuttingly adjacent to said first gear, and said bevel pinionbeing disposed abuttingly adjacent to said second gear.
 27. The assemblyof claim 26, wherein a bevel pinion is mounted within said second legand a bevel gear is mounted on an upper end of an upright elevatingscrew shaft mounted within said second leg; wherein each of said bevelpinions mesh with a corresponding one of said bevel gears attached to acorresponding one of said elevating screw shafts to simultaneouslyoperate each of said telescoping legs when said second shaft is causedto rotate.
 28. The assembly of claim 26, wherein a metal gear boxencases said pinion gear of said first shaft mounted on said first legand said high-speed drive gear; and wherein the gear box and componentsencased therein are generally adjacent to the inboard wall of said firstleg and are disposed inboard of the outboard wall of said first leg. 29.The assembly of claim 28, further comprising a crank handle secured tothe outboard end of said first shaft mounted on said first leg formanual rotation of said first shaft, wherein an intermediate portion ofsaid first shaft mounted on said first leg is formed with a transversecontinuous cylindrical opening containing a detent spring and detentballs, wherein a sleeve is mounted on an outboard face of said gear casein alignment with an opening formed in said gear case, said sleevehaving outboard and inboard annular recesses formed in an internalsurface thereof, said outboard and inboard recesses being spaced apart,wherein said detent balls engage said outboard and inboard annularrecesses when said first shaft is in the first position and secondposition, respectively, for high-speed and low speed operation,respectively.
 30. A three shaft landing gear assembly for a trailer,comprising;an input shaft, an intermediate shaft, and an output shaft,said output shaft operatively coupled to a vertically extendable andretractable trailer leg for raising and lowering the trailer, said inputshaft being axially movable between a first position for high-speedoperation and a second position for low-speed operation, a pinioncoaxially mounted on said input shaft for translating rotary motion fromsaid first shaft to said intermediate shaft, a first gear on saidintermediate shaft, said first gear having teeth which are engaged bythe teeth of said pinion gear when said first shaft is in the secondposition for low speed operation; a second gear on said intermediateshaft, said second gear having a smaller diameter than said first gear,a high-speed drive gear supported on said input shaft, said high-speeddrive gear having an axial opening with a plurality of axially extendingspline slots on its internal surface, said spline slots engaging saidpinion gear when said input shaft is in said first position, saidhigh-speed drive gear meshing with the teeth of said second gear on saidintermediate shaft when said input shaft is in said first position forhigh-speed operation; said output shaft having a drive gear coaxiallymounted thereon, said second gear of said intermediate shaft engagingsaid drive gear of said output shaft.